The present invention relates to an automotive infrared radiating lamp intended for installation on a motor vehicle and which illuminate an area forward of the vehicle with infrared light. More particularly, the invention relates to an automotive infrared radiating lamp for use together with a CCD camera having a sensitivity in a range that includes near infrared.
In a conventional lamp of the same general type as that to which the invention pertains, a visible light source and a parabolic reflector may be disposed within a lamp chamber defined by a lamp body and a front lens. An infrared transmitting filter formed by an infrared transmitting film that reflects visible light and transmits infrared light and which covers the entire surface of a glass plate is disposed between a light source and the front lens so as to entirely cover the front opening portion of the lamp chamber. Thus, the entire light output of the light source radiated in the direction of the lens passes through the infrared transmitting fillet. When the light reflected by the reflector passes through the infrared transmitting film, the visible light component thereof is cut off so that primarily only the invisible infrared component is emitted through the front lens.
An image of the infrared-irradiated area forward of the vehicle is sensed by a CCD camera which is mounted at a forward position on the motor vehicle and which has a sensitivity covering the near-infrared range. The image is processed by an image processing device, and the result displayed on a monitor screen in the passenger compartment of the vehicle. Using this system, the driver can recognize on the monitor screen the presence of persons, lane markings, obstacles, etc., even at considerable distances forward of the vehicle.
However, the infrared transmitting filter (infrared transmitting film) is not able to completely cut off long-wavelength visible light at wavelengths of about 700 to 800 nm (red light component). Therefore, together with infrared light, a portion of the visible light from the light source (red light component) is transmitted through the infrared transmitting filter and emitted through the front lens together with infrared light, so that the front lens emits red light (the lamp glows red). Hence, there is a danger of the driver of an oncoming vehicle or a pedestrian falsely recognizing a lighted infrared radiating lamp mounted at a front position of a motor vehicle as a tail lamp or a stop lamp, which gives rise to a safety problem.